A hybrid vehicle driveline may include two or more torque sources, such as an engine and a motor, for supplying torque to propel a vehicle. The torque sources may be used independently or together to propel the vehicle. In electric only mode, the motor may supply torque to the vehicle driveline while the engine remains stopped. Conversely, in engine only mode, the engine may supply torque to the vehicle driveline while the motor rotates with the engine yet provides no torque to the driveline. In still other modes, the engine and the motor may both supply torque to the driveline to meet driver demand torque.
Torque output from a motor may be estimated via current supplied to the motor. However, manufacturing and environmental variations that may introduce errors into the motor torque estimate. Likewise, engine torque may be estimated based on flow of air and fuel through the engine. However, estimated engine torque may deviate from actual engine torque due to manufacturing and environmental variations that may introduce errors into the engine torque estimate.
If the hybrid driveline is transitioned from electric only mode to engine only mode, and if either or both estimates of engine torque and motor torque are incorrect, the vehicle may accelerate or decelerate during the transition between modes. It may be possible to reduce errors in engine and motor torque via correcting engine and motor torque via torque feedback control; however, torque sensors may increase system cost and reduce system reliability.
The inventors herein have recognized the above-mentioned disadvantages and have developed a method for operating a driveline, comprising: controlling a torque converter impeller speed to a desired torque converter impeller speed based on torque converter impeller speed feedback in response to a transition in active torque sources supplying torque to the driveline.
By entering a speed control mode during a transition in powertrain operating modes, it may be possible to provide the technical result of reducing the possibility of driveline acceleration or deceleration when transitioning between powertrain modes. When the driveline is controlled in a speed control mode, speed of a driveline component is adjusted to a desired speed for the driveline component based on feedback of driveline component speed. For example, a driveline may be controlled to maintain a constant torque converter impeller speed during a transition from electric only mode to engine only mode. Speed of a motor is adjusted to maintain the constant torque converter impeller speed via adjusting an amount of current supplied to the motor. In one example, if the torque converter impeller speed is less than a desired torque converter impeller speed, motor torque may be increased so as to increase torque converter impeller speed to the desired torque converter impeller speed via supplying additional current to the motor. Similarly, if torque converter impeller speed is less than a desired torque converter impeller speed, engine torque may be increased so as to increase torque converter speed to the desired torque converter speed.
The present description may provide several advantages. In particular, the approach may reduce driveline torque disturbances of a hybrid driveline. Further, the approach may improve vehicle drivability. Further still, the approach may reduce driveline wear, thereby increasing the operating life of the driveline.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.